On the prediction of flow-induced noise at low Mach numbers: A comparative study of compressible, weakly compressible, and incompressible models

Accurate prediction of flow-induced noise at low Mach numbers (M<0.3) is hindered by the omission of weak compressibility in incompressible formulations and the heavy computational load of fully compressible schemes. To address this gap, we systematically assess an acoustic-wave-preserving weakly compressible model through three canonical cases: flow over a circular cylinder, gust–airfoil interaction, and turbulence–airfoil interaction. For benchmarking, its performance is compared against incompressible and fully compressible models, with far-field noise additionally evaluated using the Ffowcs Williams–Hawkings equation. The comparisons reveal that while all models reproduce the hydrodynamic fields, their acoustic predictions differ markedly. In particular, the weakly compressible and fully compressible models correctly capture wave propagation and provide consistent far-field noise predictions, whereas the incompressible model fails to represent acoustic radiation. Furthermore, the weakly compressible model achieves accuracy comparable to the fully compressible model for Mach numbers below 0.2, but its isentropic assumption deteriorates at higher Mach numbers. Taken together, these findings not only clarify the validity range of the weakly compressible model but also underscore the necessity of accounting for compressibility effects in low-Mach-number aeroacoustic simulations.